Severe Thunderstorm Warning 167, NWS Blacksburg, VA

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BLACKSBURG VA
654 PM EDT THU JUN 24 2010

.SYNOPSIS...
A WEAK COLD FRONT WILL MOVE THROUGH MOST OF THE AREA TONIGHT...
BEFORE STALLING NEAR THE NORTH CAROLINA BORDER. THE FRONT WILL
REMAIN NEARLY STATIONARY ACROSS NORTHWEST NORTH CAROLINA
FRIDAY BEFORE DISSIPATING...PROVIDING A FOCUS FOR SCATTERED
AFTERNOON AND EVENING THUNDERSTORMS. WEAK HIGH PRESSURE OVER THE
WEEKEND WILL BRING WARM AND HUMID CONDITIONS...WITH ISOLATED TO
SCATTERED AFTERNOON AND EVENING THUNDERSTORMS AHEAD OF A STRONGER
COLD FRONT THAT WILL MOVE THROUGH THE REGION LATE MONDAY.

&&

.NEAR TERM /THROUGH FRIDAY/...
QUICK UPDATE TO DROP THE WATCH ACROSS THE NW COUNTIES THAT ARE NOW
NW OF THE EARLIER LINE. LEFT POPS IN ACROSS THAT AREA HOWEVER AS
STILL COULD SEE A FEW CELLS POP UP AHEAD OF THE FRONT TO THE NORTH.

AS OF 215 PM...RADAR SHOWS A NEARLY SOLID LINE OF TSTMS APPCHNG
THE NORTHWESTERN MTN SECTIONS OF THE CWA. THIS LINE SHOULD HOLD
TOGETHER AT LEAST INTO OUR WESTERN SLOPES AREAS...SO I HAVE RAISED
POPS SOME MORE IN THE WEST. STILL THINKING THAT THE LINE WILL
CROSS THE CWA...SINCE EVEN MLCAPES ARE ABOVE 3000 J/KG ON THE
DOWNSLOPE SIDE OF THE MTNS. THE LINE MAY SCATTER OUT...THEN RE-
INTENSIFY IN THE PIEDMONT LEE TROUGH WHICH IS NEAR A LYH TO DAN
LINE AT THIS TIME. WILL MAINTAIN THE CHC POPS OUTSIDE OF THE
WESTERN SLOPES AREAS...THOUGH RAISE THEM SOME ALONG AND EAST OF
THE LEE TROUGH IN THE PIEDMONT. STRONG WINDS REMAIN A HIGH THREAT
WITH THESE STORMS...ESPECIALLY WESTERN SLOPES AREAS OF THE MTNS.
STORMS SHOULD BE EXITING THE PIEDMONT AREAS BEFORE MIDNIGHT. HAVE
KEPT OVERNIGHT LOWS WARM SINCE THERE IS NOT MUCH COOLER AIR BEHIND
THIS FRONT. I ALSO INCREASED THE FOG COVERAGE IN THE MTN VALLEYS.

FRIDAY...THE FRONT REMAINS STALLED ACROSS NRN N.C. NEAR THE VA
STATE LINE. HAVE INCREASED POPS A BIT ACROSS THE SRN CWA...BUT
STILL CHC AT THIS POINT...WITH NO SYNOPTIC SCALE FORCING EVIDENT.
HIGH FRIDAY WILL BE A GOOD 5 DEGREES COOLER THAN TODAY...BUT THAT
IS STILL VERY WARM...A LITTLE ABOVE NORMAL MOST LOCATIONS.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
COOL FRONT THAT IS EXPECTED TO MOVE SOUTHEAST THROUGH THE BLACKSBURG
FORECAST AREA TONIGHT INTO EARLY FRIDAY IS EXPECTED TO WASH OUT JUST
TO THE SOUTH OF THE BLACKSBURG FORECAST AREA LATER FRIDAY INTO
FRIDAY NIGHT. PROXIMITY OF SURFACE FRONT WARRANTS CONTINUED
INCLUSION OF LOW CHANCE POPS ACROSS THE SOUTHERN PERIPHERY OF THE
BLACKSBURG FORECAST AREA ON FRIDAY EVENING BEFORE ANY LINGERING
POST FRONTAL PRECIPITATION DISSIPATES WITH LOSS OF THERMODYNAMIC
SUPPORT.

WEAK SURFACE HIGH PRESSURE FORECAST TO BUILD EAST INTO THE AREA ON
SATURDAY. ATMOSPHERE IN MOST LOCATIONS SHOULD BE CAPPED OFF
SUFFICIENTLY TO SUPPORT A DRY FORECAST FOR SATURDAY INTO SATURDAY
NIGHT IN MOST LOCATIONS. EXCEPTION WILL BE ACROSS THE EXTREME SOUTH
AND SOUTHWEST SATURDAY AFTERNOON INTO SATURDAY EVENING...WHERE
INTRUSION OF DRIER AIR WILL NOT BE AS PRONOUNCED AND WHERE CAPPING
INVERSION DOES NOT MATERIALIZE. COMBINATION OF DIFFERENTIAL HEATING
DURING TIME OF BEST HEATING AND LOCALIZED UPSLOPING OVER HIGHER
TERRAIN MAY BE SUFFICIENT TO IGNITE AN ISOLATED STORM OR TWO.

NEXT IN WHAT WILL BE A SERIES OF STRONG UPSTREAM SHORT WAVE TROFS IN
THE NORTHERN STREAM WILL PUSH INTO THE UPPER GREAT LAKES ON
SUNDAY...ALLOWING LOWER TROPOSPHERIC FLOW TO BACK MORE INTO THE
SOUTHWEST...ADVECTING WARMER AND INCREASINGLY MOIST AIR BACK INTO
THE REGION. WILL AGAIN RUN THREAT OF DIURNALLY-DRIVEN
SHOWERS/THUNDERSTORMS SUNDAY AFTERNOON INTO SUNDAY EVENING...WITH
HIGHEST POTENTIAL FOR ACTIVITY OVER THE SOUTHWESTERN UPSLOPE AREAS
WHERE POTENTIAL TEMPERATURES WILL BE MAXIMIZED AND WHERE LAPSE RATES
WILL BE THE MOST UNSTABLE IN UNCAPPED ENVIRONMENT.

MOS GUIDANCE FOR DAYTIME HIGHS AND OVERNIGHT LOWS CAME IN REMARKABLY
SIMILAR...BUT UNDERCUT BOTH NIGHTTIME LOWS AND DAYTIME HIGHS JUST A
TAD IN ALL AREAS...MOST NOTABLY IN THE MOUNTAINS...TO OVERCOME
PERSISTENT WARM BIAS DEMONSTRATED DURING THE PAST SEVERAL DAYS.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
LONG TERM PERIOD WILL BE CHARACTERIZED BY SLOWLY AMPLIFYING UPPER
TROF THAT WILL BECOME ESTABLISHED OVER THE NORTHEASTERN PART OF THE
NATION FOLLOWING PASSAGE OF A SERIES OF STRONG SHORT WAVE TROFS IN
THE NORTHERN STREAM MONDAY INTO MONDAY NIGHT. RELATIVELY DEEP
WESTERLY LOWER TROPOSPHERIC WINDS OVER THE MID APPALACHIANS PRIOR TO
ARRIVAL OF COLD FRONT WILL SUPPORT DEVELOPMENT OF A LEE TROF TO THE
EAST OF THE BLUE RIDGE SUCH THAT ANY SHOWERS/THUNDERSTORMS IN
VICINITY OF APPROACHING FRONT SHOULD BE MAXIMIZED ALONG THE WESTERN
UPSLOPE AREAS FROM SOUTHEASTERN WEST VIRGINIA SOUTH INTO THE
MOUNTAINS OF NORTH CAROLINA...AND ACROSS SOUTHSIDE VIRGINIA INTO
NORTH CENTRAL NORTH CAROLINA...WITH A RELATIVE MINIMUM...ALBEIT
STILL LOW THREAT POPS...EAST OF THE ALLEGHANY HIGHLANDS OUT TOWARD
THE LYNCHBURG AREA.

WILL GRADUALLY END THREAT OF POST FRONTAL SHOWERS/THUNDERSTORMS FROM
THE NORTHWEST ON TUESDAY...AND ACROSS THE EXTREME SOUTH (WHICH WILL
BE CLOSEST TO EXITING FRONT) ON TUESDAY NIGHT...TO BE FOLLOWED BY
DRY AND COOLER FORECAST WEDNESDAY AND THURSDAY AS SURFACE HIGH
PRESSURE BUILDS SOUTHEAST INTO NEW ENGLAND...AND RIDGES SOUTHWEST
INTO THE MID ATLANTIC STATES EAST OF THE BLUE RIDGE.

LONGER RANGE MODELS IN A BIT OF DISAGREEMENT IN EXTENT AND DURATION
OF UPPER TROFFING OVER NORTHEASTERN PORTION OF THE NATION DURING THE
LATTER PART OF THE PERIOD. THE ECMWF NOT AS AGGRESSIVE IN AMPLIFYING
UPPER TROF OVER TIME AND DOES NOT INFUSE IT WITH ADDITIONAL UPSTREAM
ENERGY...WHICH SUPPORTS FLATTER AND MORE PROGRESSIVE TROF AND WHICH
ALLOWS UPPER RIDGE AND INCREASING HEAT AND HUMIDITY TO ADVANCE EAST
OUT OF THE CENTRAL PLAINS BY LATE IN THE PERIOD. ECMWF DEPICTION
GENERALLY DISCARDED WITH RESPECT TO GFS AND ENSEMBLE MEAN CLUSTERS
CONSIDERING THAT LATEST RUN OF ECMWF A DISTINCT OUTLIER AND
INCONSISTENT WITH ITS OWN LAGGED AVERAGES.

WITH THE ABOVE IN MIND...FAVORED THE COOLER HPC GUIDANCE THROUGHOUT
THE LONG TERM PERIOD...WITH ONLY SLIGHT TWEAKS MADE TO REFLECT LOCAL
CLIMATOLOGICAL INFLUENCES.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
EARLIER CONVECTIVE LINE HAS SPLIT IN THE MIDDLE WITH BEST COVERAGE
MAINLY SW OF THE TAF SITES EARLY THIS EVENING WITH ISOLATED STORMS
NEAR KDAN AND KLYH. MAY SEE THE LINE COME BACK TOGETHER ACROSS THE
SOUTH IN THE NEXT COUPLE OF HOURS BEFORE PUSHING SOUTH AND FADING
WITH LOSS OF HEATING. THUS WILL KEEP A TSRA VICINITY OR TEMPO
MENTION GOING ACROSS THE EASTERN SITES AND PERHAPS AN ISOLATED
SHOWER THAT MAY REDEVELOP OVER THE NW AHEAD OF THE ACTUAL FRONT.

MOST SITES WILL LIKELY SEE AT LEAST MVFR FOG DEVELOP. WITH A
LIGHT WEST FLOW INTO THE MTNS...BLF AND LWB WILL LIKELY DROP TO
IFR OR LIFR. CONDITIONS WILL IMPROVE QUICKLY EAST OF THE MTNS
FRIDAY MORNING...AND MORE SLOWLY IN THE MTNS WITH THE LIGHT WEST
WIND. BLF AND LWB WILL LIKELY NOT LIFT TO VFR UNTIL 15Z...POSSIBLY
LATER.

ON FRIDAY...THE FRONTAL BOUNDARY MAY STILL BE ACROSS SOUTHERN
PORTION OF THE AREA...WITH BEST CHANCES FOR MORE CONVECTION AND
TEMPORARY AFTERNOON/EVENING RESTRICTIONS TO VSBYS/CIGS AT DAN AND
MAYBE AS FAR NORTH AS ROA. BY SATURDAY...THE FRONT IS LIKELY TO
HAVE PUSHED FAR ENOUGH TO THE SOUTH TO KEEP CONVECTION SUPPRESSED.
BY SUNDAY SOME DEGREE OF MOISTURE RETURN AS FRONT TO SOUTH WASHES
OUT SO WILL ONCE AGAIN SEE AIR MASS TYPE DIURNAL
THUNDERSTORMS...BUT MAY BE VERY ISOLATED. THEN PERHAPS MORE
WIDESPREAD STORMS AHEAD OF ANOTHER COLD FRONT BY MONDAY.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.

&&

SYNOPSIS...JJ
NEAR TERM...JJ
SHORT TERM...WERT
LONG TERM...WERT
AVIATION...JH/JJ/SK

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE BLACKSBURG VA
646 PM EDT THU JUN 24 2010

VAZ007-010-011-018>020-WVZ042>045-252300-
TAZEWELL-BLAND-GILES-CRAIG-ALLEGHANY VA-BATH-MERCER-SUMMERS-MONROE-
GREENBRIER-
646 PM EDT THU JUN 24 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHWEST VIRGINIA...WEST
CENTRAL VIRGINIA AND SOUTHEAST WEST VIRGINIA.

.DAY ONE...TONIGHT.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

NCZ001-002-018-VAZ009-012>017-022>024-032>035-043>047-058-059-252300-
ASHE-ALLEGHANY NC-WATAUGA-SMYTH-WYTHE-PULASKI-MONTGOMERY-GRAYSON-
CARROLL-FLOYD-ROANOKE-BOTETOURT-ROCKBRIDGE-PATRICK-FRANKLIN-BEDFORD-
AMHERST-HENRY-PITTSYLVANIA-CAMPBELL-APPOMATTOX-BUCKINGHAM-HALIFAX-
CHARLOTTE-
646 PM EDT THU JUN 24 2010

...SEVERE THUNDERSTORM WATCH 408 IN EFFECT UNTIL 10 PM EDT THIS
EVENING...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHWEST NORTH
CAROLINA...CENTRAL VIRGINIA...SOUTH CENTRAL VIRGINIA...SOUTHWEST
VIRGINIA AND WEST CENTRAL VIRGINIA.

.DAY ONE...TONIGHT.

PLEASE LISTEN TO NOAA WEATHER RADIO OR GO TO WEATHER.GOV ON THE
INTERNET FOR MORE INFORMATION ABOUT THE FOLLOWING HAZARDS.

   SEVERE THUNDERSTORM WATCH.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED.

NCZ003>006-019-020-252300-
SURRY-STOKES-ROCKINGHAM-CASWELL-WILKES-YADKIN-
646 PM EDT THU JUN 24 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH CENTRAL NORTH CAROLINA
AND NORTHWEST NORTH CAROLINA.

.DAY ONE...TONIGHT.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.

SCATTERED STRONG TO SEVERE THUNDERSTORMS MAY DEVELOP IN THE AREA
FRIDAY AFTERNOON. DAMAGING WINDS WOULD AGAIN BE THE MAIN THREAT.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED.

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